As the value and use of information continues to increase, individuals and businesses seek additional ways to process and store information. One option available to users is information handling systems. An information handling system generally processes, compiles, stores, and/or communicates information or data for business, personal, or other purposes thereby allowing users to take advantage of the value of the information. Because technology and information handling needs and requirements vary between different users or applications, information handling systems may also vary regarding what information is handled, how the information is handled, how much information is processed, stored, or communicated, and how quickly and efficiently the information may be processed, stored, or communicated. The variations in information handling systems allow for information handling systems to be general or configured for a specific user or specific use such as financial transaction processing, airline reservations, enterprise data storage, or global communications. In addition, information handling systems may include a variety of hardware and software components that may be configured to process, store, and communicate information and may include one or more computer systems, data storage systems, and networking systems.
Certain information handling system, such as notebook computer systems, are designed to operate on battery power and/or power from a powered outlet. With respect to battery operation, end-user customers often demand that batteries must charge quickly and last for many charging cycles. For example, with respect to information handling systems available from DELL, these customer demands have been translated to requirements that the battery be charged to 80% of its charge capacity within one hour, that the battery be fully charged within two-hours, and that the battery have at least 75% of rated capacity after 300 charging cycles. Unfortunately, the faster a battery is charged during its charging cycles, the faster its capacity decreases over time. When the capacity decreases, the relative charge rate increases. This increase makes the capacity decrease even faster. In previous generations of batteries (e.g., 1.6, 1.8, 2.0, 2.2 and 2.4 Ampere hours (Ah)) there has typically been enough design margin to overcome this problem. However, the generation of cells currently under development (e.g., 2.6 Ah and beyond) are typically being optimized for initial charge capacity, and so they cannot maintain cycle life performance at high charge rates.
With certain charging methods currently in use, the battery is charged at a constant charge current or rate until it reaches a maximum voltage. The charger then maintains this maximum voltage while continuing the charging process (e.g., using pulsed charges) until the current decreases to a preset limit at which time the charging cycle concludes. Typically, the constant current and maximum voltage do not change as the battery ages and loses charge capacity, so the charge rate effectively increases as the battery ages. For example, if a fixed charge current is selected based upon initial charge capacity (C) such that the charge current will charge the battery to 80% of its capacity within one hour (which is designated as a charge current or rate of 0.8 C), the effective charge current will increase as the battery charge capacity degrades over time. For example, a battery that initially has 5.2 Ah of capacity may be charged at a fixed charge current of 0.8 C or 4.16 A (i.e., 80% in one hour times 5.2 Ah). After 100 cycles, however, the capacity may have dropped, for example, to a new charge capacity (CNEW) of about 4.6 Ah. The charge rate is still constant, however, at 4.16 A thereby making the effective charge rate about 0.9 CNEW. Thus, as the battery ages and its charge capacity degrades, the battery is being charged at an ever increasing effective charge rate. This increased charge rate then further hastens the degradation in charging capacity because the battery is being effectively charged faster and faster. Reducing the charge rate (e.g., to about 0.5 C) may allow the battery to meet cycle life requirements by reducing the amount of capacity loss; however, the battery may no longer meet desired charge time requirements. Thus, the current fixed charge current solutions for charging batteries are not effective solutions.